Gases originating from sulfur-containing organic compounds contain hydrogen sulfide, which should be removed prior to the use of the gases for a process such as the production of phosgene. Hydrogen sulfide can be partially removed from a gas by passing the contaminated gas over activated carbon, wherein the hydrogen sulfide is physically adsorbed into the pores of the activated carbon. The sulfur produced is adsorbed on the surface of the activated carbon, and eventually the activated carbon needs to be replaced or regenerated due to sulfur loading on its surface.
Phosgene, COCl2, is produced by the reaction of carbon monoxide gas, CO, and chlorine gas, Cl2, over activated carbon. The carbon monoxide gas used in the reaction is typically produced from coke, and is usually contaminated by a number of sulfur compounds, including carbonyl sulfide (COS), carbon disulfide (CS2), and hydrogen sulfide (H2S). Before the carbon monoxide gas stream enters the phosgene reaction container, activated carbon is used to treat the gas steam and hopefully to remove these sulfur compounds from the gas. The capacity for activated carbon to remove H2S, however, is less than its capacity to remove most other sulfur compounds. As a result of this lower capacity for H2S removal, H2S breaks through the activated carbon. That is, H2S is not removed from the carbon monoxide gas stream entering the phosgene reaction container, at a time when the carbon is not exhausted with respect to its capacity to remove the other sulfur compounds. Several disadvantages occur as a result of the premature exhaustion of the activated carbon with respect to H2S removal. One problem is that sulfur deposits on the phosgene catalyst in the reaction chamber. Another problem is that deposits of sulfur foul the downstream equipment, such as the CO/Cl2 mixing area, the phosgene reactor, and the phosgene condenser. In addition, there is loss of productivity because of the need to frequently interrupt the synthesis process in order to remove the activated carbon and regenerate or replace it. Therefore, a need exists for a more efficient system to remove sulfur compounds from carbon monoxide gas before it enters a synthesis reaction.